Grid-Following vs. Grid-Forming

The fundamental difference between grid-following and grid-forming systems lies in their reliance on and contribution to the power grid, analogous to "followers" and "co-builders" of the grid.

Grid-following energy storage systems function essentially as "current sources," depending on grid voltage and phase references for stable operation, much like "followers" synchronizing to the rhythm of the grid.

Grid-following energy storage systems feature simple control logic and low equipment costs, making them well-suited for scenarios with stable grid structures. These include distributed photovoltaic power generation and energy storage, as well as peak shaving and valley filling for industrial and commercial users—situations that do not require additional grid support.

Grid-forming energy storage systems use algorithms to configure the converter as a "voltage source," exhibiting external characteristics similar to those of a synchronous generator. This enables the system to autonomously provide voltage and phase references, as well as deliver inertia, damping, and short-circuit current to support the grid.

The advantage of this technology lies in its exceptional grid support capabilities, including rapid frequency and voltage regulation, suppression of low-frequency oscillations, and even black-start functionality. These features make it indispensable for grids with a high penetration of new energy sources.

Grid-forming energy storage technologies must meet stringent requirements for overload capacity (300% of rated current for 10 seconds), inertial response (start-up time ≤ 50 ms), and voltage support (reactive response ≤ 10 ms).